The root cause is Streptococcus mutans and other bacteria in the mouth. Dentists would be out of business, except for trauma injuries, if these bacteria were eliminated.

Ellie Phillips has this triple mouthwash system, in her book "Kiss your dentist goodbye". Apparently she hasn't had her teeth cleaned in 40 years. I have been using it and it seems to work, in that my dentist says I have the best teeth out of all his patients despite me brushing my teeth maybe once a week. The motivation for the mouthwash is simply that mechanical brushing isn't sufficient to kill the bacteria, whereas mouthwash is if you can disrupt all of the biofilms. And then the other two mouthwashes are for pH and fluoride.

And the peer reviewed science for this being true is where? Sorry personal anecdotes don't count

There are references in her book. The effects of pH and so on have been well-studied, and antibacterial mouthwashes are well-known to kill bacteria. I don't think there's been an RCT or anything of her system specifically, so that is based on her experience, but the studies do demonstrate that brushing alone is not sufficient. I'm not saying she's the last word on the subject, but it's how evidence-based medicine works - if you don't have strong evidence, you look at weak evidence such as expert advice, and I haven't found any other advice that discusses going beyond brushing. That's sort of the issue, is that (similarly to this neurosurgeon's experience) the vast majority of dentistry is focused on filling cavities, rather than promoting oral health or health in general.

Ellie Phillips is a big fan of xylitol though. The science on that is a lot less clear, e.g. how much xylitol is necessary in gum (she of course advocates huge amounts), and then she also sells mints which have little effect on plaque. (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8791908/) I sort of ignore that, just because she has to make money doesn't mean the rest of her advice is not evidence-based.

On the small scale, this might be true. But on the larger scale, there's much, much more money to be made from fixing the problem after the fact.

Edit: If dentistry as an industry cares, so, so much about dental care then why are they not lobbying for less sugar in our food? Is providing care and regular advice the most effective way to fix the problem?

The fix is easy, stop giving kids so much goddamn sugar as a system.

We give adults way too much sugar as well. Every goddamn drink has shittons of sugar. Even a goddamn bread loaf has added sugar these days. A cup of many brands of flavored yogurt have half the sugar as a coke, and they try to pass yogurt off as the "healthy" alternative to ice cream. It's the same if it has the same amount of sugar. The coffee shop near my place sells 5 types of flavored lattes. They all have added sugar. The Japanese, Chinese, and western bakeries near me have added sugar in every pastry and every drink. It's fucking insane.

There is absolutely no need for this. It desensitizes everyone to sugar AND makes them addicted so that you can sell them more junk with even more sugar.

Sugar is a problem. A hundred or so years ago, you may eat a pound or five of sugar over a year. We are now eating like 40lbs a year.

But sugar is not the only problem. Why do ancient skeletons all (mostly) have great, straight teeth and strong jaws? That is not sugar. I suspect it is soft foods.

You are missing the forest for the trees here